Audio playback devices become more and more important. Particularly, audio systems comprising audio manipulating features become more and more important.
U.S. Pat. No. 5,742,687 discloses a signal combining circuit having a first input and a second input for receiving signals which have frequencies in the audio frequency spectrum, and an output. A first signal path between the first input and the output has a first transfer characteristic. A second signal path between the second input and the output has a second transfer characteristic. The transfer characteristics are different which causes a phase shift to occur between signal components passed through the first signal path and signal components passed through the second signal path. The amplitude transfer determined by the transfer characteristics decreases above a predetermined frequency. There is a phase difference between phase transfer characteristics which decreases with frequency. For frequencies below the predetermined frequency the amplitude transfer determined by the first transfer characteristic exceeds that determined by the second transfer characteristic. By interconnecting the first input and the second input, the amplitude transfer between the interconnected inputs and the output as a function of frequency is substantially constant. The signal combining circuit is used in a stereophonic audio reproduction system to enhance the stereo image. The stereophonic audio reproduction system can form part of an audio-visual reproduction system.
However, it may happen with conventional audio playback systems that the audio playback quality is not satisfactory.